The present invention relates to a foot prosthesis comprising a front foot portion, a rear foot portion and an intermediate foot portion formed by a number of rods of flexible and resilient material, which rods extend in the longitudinal direction of the foot prosthesis.
A foot prosthesis of the above mentioned type is known through WO 98/01092. In the known foot prosthesis, the rods are fixed to the front and rear foot portions. A such prosthesis functions well during use on an even ground but worse on an irregular ground where the different portions may need to pivot relative each other around longitudinal axes.
The present invention aims to improve a foot prosthesis of the above mentioned type so that the different foot portions can be easily rotated relative each other around longitudinal axes and to provide a foot prosthesis which characteristics can be easily adjusted to the needs of different users.
These aims are achieved by a foot prosthesis comprising a front foot portion, a rear foot portion and an intermediate foot portion formed by a number of rods of resilient material, which rods extend in the longitudinal direction of the foot prosthesis, characterized in that the rods are rotatably connected to the front and rear foot portions. By the rotatable connection of the rods, a rotation of the front and rear foot portions relative each other is not hindered by torsion forces from the rods, but are only exposed to bending forces. Besides facilitating rotation of the prosthesis portions relative each other it is easy to ad just the characteristics of the foot prosthesis to different users as the only thing that has to be taken into consideration in such an adjustment is the bending resistance of the rods. Nor will the rods exert any torsional force to the material in the connections to the front and rear foot portions, which eliminates the risk of endurance failure in these connections.
In a preferred embodiment the front and rear foot portions comprise sleeves of low friction material for receiving the rods and the rods have a circular cross section. At least one of the rods can have a different bending resistance from the other rods. The rear foot portion comprises an elongated element, which protrudes above the rods and which is vertically located at a distance above the rods in their resting position and which restricts the bending deformation of the rods. Further, the foot prosthesis comprises a cover of flexible material, which surrounds the foot portions so that axial displacement of the front and rear foot portions relative each other is substantially prevented and the rear foot portion comprises a heel section, which is rotatable around a central, longitudinal axis. Advantageously, the heel section comprises an element of resilient material, which extends between a lower heel plate and an upper part of the rear foot portion.